Considering how incredibly buggy this is, perhaps it could be changed to a 1/day player tool that gives 10 Temporary HP when used, so it won't expire on first transition and therefore be useless? Or some other bonus like 1/- DR for 10 HP worth of damage?
Sounds good. I think the temp hp over the dr though as it would have no effect on barbarians.
It would work just fine on barbs because they get DI as a class feature not DR. It wouldn't work with Thug or werecreature though.